“My smart plug ignores Nord Pool prices”: the standby-at-0% rule a Latvian customer taught us to explain
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Every product has one setting that its makers find obvious and its users find invisible. For the GPO Smart Plug it is the base state. A customer in Latvia found it the hard way, wrote to us with screenshots, and his email became the outline of the setup guide we should have had from day one. This article is that guide, told through his case.
The customer's problem
He bought the plug to run his water boiler for at most five hours a day in the cheapest Nord Pool intervals. The plug did not react to prices at all: it stayed on the whole time, including when electricity was expensive. His own reading of the logic was right in principle ("the socket should be off by default and the Nord Pool mode switches it on for 5 hours"), but he could not find anywhere in the app what "ON 100%", "75%" and the other values meant. His closing request: add hints, because this is not easy to understand without experience.
What we did
We answered within a day with two commitments: check his configuration and look for a bug on our side, and add in-app hints plus a short setup guide for the Nord Pool mode. This article is that guide, and its core is simple enough to fit in a paragraph.
The rule, explained
The plug has a base state (what it does outside the selected hours) and a Cheap Mode action (what it does inside them). For a boiler: base state = ON at Manual 0%, action = ON – 100%, condition = Working hours with the number of hours you want. OFF is not a valid base state, because a switched-off plug ignores every schedule. The percentages are the share of time power is on within a repeating 5-minute cycle: 100% is continuously on; 75% is 3 min 45 s on and 1 min 15 s off; 50% is 2 min 30 s each; 25% is 1 min 15 s on; 0% is powered but delivering nothing. Those intermediate values exist for heaters (a soft power limit); for a boiler or a charger you use only 0% and 100%.
Benefit for the customer
With the base state set correctly, a boiler runs only in the selected hours, and the Statistics screen shows consumption only inside those windows. Five hours is generous for most tanks; we recommend starting from the time a full tank needs from cold (about 2–3 hours for 80 L / 2 kW) because every additional hour is bought at a progressively worse price.
Technology used
Nord Pool day-ahead prices for Latvia, 15-minute resolution, schedule recalculated daily and pushed to the plug online; per-interval consumption logging; overload protection at 16 A with a push notification; Bluetooth fallback up to 50 m when there is no Wi-Fi. Works with any exchange-price contract (Elektrum, Enefit, Ignitis, Fortum and others).
Improvements and know-how
From this and the Tallinn boiler case we wrote this guide and committed to in-app hints for "Apply for devices" and the power ratio. The deeper lesson is about defaults: the app should not let a user activate Cheap Mode while the base state would block it. A warning at activation time is in the plan; the stronger fix is the two-control screen described in the Tallinn case. One more rule from multi-plug households: heaters should use the Price threshold condition instead of Working hours (see the multi-plug household article).
What's next
Latvian customers already buy several plugs at once (see the multi-plug household article). We plan to translate this guide into Latvian, Estonian, Lithuanian and Finnish so that the base-state rule is readable in the customer's own language before the first setup.
FAQ
What does "ON 75%" mean? Power on for 75% of each 5-minute cycle. Useful for heaters, not for boilers.
Do I set the plug to OFF so Cheap Mode can turn it on? No. Set it to ON with Manual 0%. OFF overrides Cheap Mode.
How do I see that it works? The price chart highlights today's selected hours; from the next day, Statistics shows consumption inside them and zero outside.
Where to get it
GPO Smart Plug: GPO Smart Plug for spot price automation (€35).